The present invention relates to an anchoring device used for fastening an object to a supporting structure. More specifically,the invention relates to an anchoring device for anchoring in porous construction materials, particularly aerated cement and hollow structural blocks.
Known anchoring devices or expansion dowels of the type under consideration comprise a slotted expansion sleeve provided with an expandable member having an expansion cone, which is movable in the axial direction of the sleeve by means of a screw.
Anchoring devides of the type under discussion are disclosed, for example, in the applicant's U.S. Pat. Nos. 3,277,623; 3,082,657; 3,524,379; 3,815,467; 4,094,054; 4,094,223; 4,182,091; 4,065,996 and 4,050,346.
Expansion dowels known in the art are usually utilized for anchoring in hard solid construction materials in which, in order to achieve effective anchoring, relatively small expansion is required. If such elements are to be inserted in porous construction materials, such as aerated cement or hollow construction block, it is necessary to use, due to insignificant expansion abilities of known expansion dowels, the expansion sleeve of the double wall thickness as compared to that which is normally used, in order to provide only relatively small holding or anchoring forces.
Since the wall thickness of the expansion sleeve defines the expansion quality of the anchoring device there have been suggested special dowels of very large outer diameters for porous construction materials. The utilization of such dowels, however,caused difficulties during the assembly and required that a hole, which is usually formed in masonry or supporting structure to receive the expansion dowel therein, would be also of a larger diameter as well as the diameter of the fastening or actuating screw which is inserted into the dowel. Frequently, however bores or holes for fastening objects to the supporting structure, such as masonry, are preliminarily made in the masonry; these bores do not allow, however, drilling of holes of larger diameters to receive expansion sleeves of larger diameters therein.